principle-model-the-domain
About principle-model-the-domain
A development skill for representing domain rules in data structures instead of spreading them across conditionals. It helps developers choose models that prevent invalid states while avoiding abstractions that add indirection without reducing complexity.
Key features
- 01Represent domain rules in structures
- 02Use state machines and typed models
- 03Replace scattered branches with registries
- 04Avoid abstractions without clear benefits
Use cases
- 01Reshape code with growing conditional chains
- 02Represent lifecycle and state constraints
Install
Copy the command and run it in a terminal.
npx skills add https:/After installing, type/principle-model-the-domainin Claude Code to confirm it loaded.
Details
From the project READMEModel the Domain
Encode the real domain in a data structure instead of scattering it across conditionals. A structure that matches the domain makes invalid states unrepresentable and deletes branches. Choosing it at write time is cheap. Recovering it later reads as a refactor and gets deferred.
Reach for:
- A state machine instead of scattered booleans, phases, or lifecycle checks.
- A typed model instead of loose parameters or repeated shape assumptions.
- A map, registry, lookup table, or discriminated union instead of branching spread across files.
- A reducer or command/event model instead of ad hoc state mutations.
- A module organized around one body of domain knowledge instead of a sequence such as load, validate, transform, and save. Execution order is not ownership.
- A small module boundary that gathers repeated behavior, ownership, or invariants.
- A queue, cache, index, graph, tree, or normalized collection where the access pattern calls for it.
- Any other structure that fits. When none fits, work out what the code must never allow and how the data gets read, then find the structure that encodes exactly that.
Do not force an abstraction. Prefer boring code if the current shape is already clear, local, and unlikely to grow. Be skeptical of an abstraction that adds indirection without removing branches, duplicated rules, invalid states, or lifecycle risk.
The sign that you skipped this is a new feature that grows an existing if/else chain by one more branch, or a second boolean that must stay in sync with the first. Temporal decomposition is another sign. Phase-named modules repeat the same domain rules across steps.